Comparison of Two Capture Methods for Endoscopic Removal of Large Common Bile Duct Stones

Introduction

Endoscopic sphincterotomy followed by balloon dilation is an established method for the extraction of large common bile duct (CBD) stones. ¹ Many studies have confirmed the applicability of this method as an alternative technique for the management of large bile duct stones associated with a favorable outcome.^2–8 Although endoscopic sphincterotomy followed by balloon dilation has been found in a few studies to have a higher stone clearance success rate, reported to range between 94% and 99%,^3,4,7,9 the success rate of most reports varies between 60% to 90%.^2,7,10–16 The factors influencing the results of stone clearance have been investigated in previous studies, which have shown that failure of endoscopic stone extraction is more frequent among patients with a large bile duct stone. ¹⁷ A large stone size is also an important predictor for unsuccessful clearance.^12,13 Stone impaction in the bile duct was also indicated as a key predictor of stone clearance failure. ¹⁸ However, stone impaction is frequently observed in patients with large stones. ¹³ Regardless of the chosen endoscopic procedure, large stone extraction is a major concern due to high failure rates, even for experienced endoscopists. ¹ Many studies have indicated that the failure of stone clearance is mostly due to inability to capture the stone.^{8,10,12,14,19} Therefore, effective capture is a critical step for the successful removal of large stones. However, to date, we have not found any literature evaluating techniques for the capture of large CBD stones. After repeatedly failing to capture large stones, we evaluated two popular techniques. The aim of the present study is to compare the success rate of the two methods for the removal of large CBD stones.

Patients and Methods

Methods

ERCP was performed in 531 patients with CBD stones shown by MRCP; 67 of these patients had a maximum stone diameter of ≥20 mm. The study was designed as a prospective, randomized with crossover, observational clinical trial. Patients were randomized to undergo either Method A (Group A) or Method B (Group B), using a table of random numbers. A resident doctor assigned a number from the table to each patient entering the study. Patients given an odd number received Method A, and patients given an even number received Method B. For Method A (33 cases), the basket was inserted above the large stones, opened, and moved up and down. ²⁰ For Method B (34 cases), the basket was stretched out from the bottom of the stones and opened slowly, upward from below. Patients who failed to have the common duct cleared of stones with Method A were reassigned to treatment with Method B. The study was approved by our institutional ethical review. All patients provided written informed consent before entering the study.

We made an incision to the midportion of the papilla with a pull-type sphincterotome and then inserted a balloon (20 mm in diameter; Wilson-Cook Medical, Winston-Salem, NC) over a guide wire. Balloon dilation was performed using wire-guided hydrostatic balloon catheters placed across the papilla (Fig. 1A and B). Using Method B, for single stones, the basket was stretched out from the bottom and pushed up to trap the stone. For multiple stones and permeated stones, insertion of the basket into the proximal CBD was avoided. As shown in Figure 2, the basket was stretched out from the distal CBD and opened slowly. During this process, the endoscope should be rotated counterclockwise repeatedly in order to push the opened basket to trap the stones. After the stones were trapped in the basket, they were extracted from the biliary tract (Fig. 1C). In cases where the stone could not be extracted from the biliary tract, the Teflon^® (Dupont, Wilmington, DE) sheath of the basket was replaced with a metal sheath, and mechanical lithotripsy (Endo-Flex^®, Voerde, Germany) was performed to fragment the stones. After the fragmented stones in the distal CBD were removed (Fig. 1D), the stones remaining in the proximal CBD were captured and crushed using Method B again. When the stones in the proximal CBD were captured, mechanical lithotripsy was carried out, and the lithotripsy basket was withdrawn. If the bile duct stones were retrievable, their composition was analyzed by sonography or computed tomography of the abdomen using a method described by Tsai et al. ²¹ The stones were classified as cholesterol or bilirubinate stones according to the predominant composition. The success rate of the first method used was recorded for this trial.

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FIG. 1.

Endoscopic view. (A) Papillary dilation with a 20-mm large balloon after endoscopic sphincterotomy. (B) Dilated orifice after endoscopic sphincterotomy plus endoscopic papillary large balloon dilation. (C) The large stone was removed without crushing. (D) Stones were removed after mechanical lithotripsy.

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FIG. 2.

Fluoroscopic images of Method B. (A) Fluoroscopic view of permeated stones. (B) The basket was stretched out from the distal common bile duct. (C) The basket was opened, and the stone in the distal common bile duct was captured successfully. (D–F) After the stones in the distal common bile duct were taken out, the stones that existed in the proximal common bile duct were captured and crushed in turn using Method B.

Results

Of the 531 patients with CBD stonesindicated by MRCP, 466 patients were excluded, and 67 patients were included. In Group A, 11 cases were captured successfully with Method A, and the success rate was 33.3%. In Group B, 32 cases were captured successfully with Method B. Thus the success rate of Method B in Group B was 94.1%. Based on this success rate, Method B again was adopted to treat failed cases in Group A, and 21 cases were captured successfully. There was one failure cannulation in each group, respectively. The overall of Method B in the two groups was 96.4%. There was a significant difference in the success rate of capturing stones between the two groups (P<.05). The 7 cases with impacted large stones in the two groups were successfully captured using Method B. All stones successfully captured were directly removed (25 cases) (Fig. 1C) or removed after mechanical lithotripsy (38 cases) (Fig. 1D). A second procedure to achieve complete clearance was used in 12 patients in Group A and 13 patients in Group B. After ERCP, 7 patients had mild pancreatitis, and 2 patients had mild bleeding, returning to normal after conservative treatment. There was no significant difference between the two groups for major complications, such as pancreatitis, perforations, or hemorrhages (P>.05). The success rate, composition of the stones, and complications are presented in Table 2.

Discussion

The factors influencing the success rate of stone clearance have drawn considerable attention.^10,22 Several reports indicate that large stones could also be successfully captured and crushed.^5,8,9,19 However, very large stones often make mechanical lithotripsy cumbersome or even impossible. ²³ There have also been numerous reports about the failure to capture large stones.^{4,8,10,12,24,25} Cipolletta et al. ²² reported that mechanical lithotripsy failed in 16.0% of patients with large stones, which was primarily due to inability to capture the stone within the basket. Kim et al. ² also reported similar results. The primary reason reported for the failure is insufficient space in the CBD to properly open the basket to capture the stone despite the fact that the basket wires may slip around the stone.^26–28 Unfortunately, these reports did not mention if the failure in the capture of large stones correlated with the capture method. We believe that failure to capture large stones is likely to be associated with the method used. In the present study, the success rate of capturing stones was compared between two methods. Our findings demonstrated that the success rate of Method B was significantly higher than with Method A. As described above for Method B, the basket was stretched out from the bottom of the distal CBD and pushed up to engage the stone, which was different from Method A, in which the basket is inserted above the stone and pulled down in order to capture it. The high success rate of this new method could be explained by the empty distal CBD when the stones in the distal CBD are moved up to facilitate opening the basket. Moreover, when the basket encounters resistance from the proximal CBD, it is more easily opened because of driving force from below. Ten patients with stones >3 cm (the largest was 4.8×3.1 cm) (Fig. 3) were successfully captured. In our study, the proportion of bilirubinate stones was 87.9% in Group A and 91.2% in Group B, which might have a small influence on the success rates of the two methods. However, the key factor for the successful removal of larger stones is the ability to capture the stones. Our findings indicate that Method B is more successful for the removal of these large stones.

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FIG. 3.

Fluoroscopic images of capturing and crushing a large stone (4.8×3.1 mm) with Method B. (A) Fluoroscopic view of one huge stone. (B) The large stone was captured successfully using Method B. (C) The large stone was crushed by mechanical lithotripsy.

Method B was used to relieve the stone blockage because after the injection of contrast media, pushing the basket can loosen impacted stones. This was different from previously reported methods.^13,23,29 The impacted large stone in 7 cases in our study was successfully captured using this method.

When findings are taken together, Method B was clearly the method of choice for the management of large CBD stones. Future studies in a large cohort of patients should be performed to confirm our findings.